linux-kernel - [PATCH v3] rtc: ds1307: provide an indication that the watchdog has fired

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Date:   Mon, 27 Jul 2020 15:46:14 +1200
From:   Chris Packham <chris.packham@...iedtelesis.co.nz>
To:     a.zummo@...ertech.it, alexandre.belloni@...tlin.com,
        linux@...ck-us.net
Cc:     linux-rtc@...r.kernel.org, linux-watchdog@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Chris Packham <chris.packham@...iedtelesis.co.nz>
Subject: [PATCH v3] rtc: ds1307: provide an indication that the watchdog has fired

There's not much feedback when the ds1388 watchdog fires. Generally it
yanks on the reset line and the board reboots. Capture the fact that the
watchdog has fired in the past so that userspace can retrieve it via
WDIOC_GETBOOTSTATUS. This should help distinguish a watchdog triggered
reset from a power interruption.

Signed-off-by: Chris Packham <chris.packham@...iedtelesis.co.nz>
---
Changes in v3:
- Check for watchdog flag in ds1307_wdt_register()
Changes in v2:
- Set bootstatus to WDIOF_CARDRESET and let userspace decide what to do with
  the information.

 drivers/rtc/rtc-ds1307.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/rtc/rtc-ds1307.c b/drivers/rtc/rtc-ds1307.c
index 49702942bb08..54c85cdd019d 100644
--- a/drivers/rtc/rtc-ds1307.c
+++ b/drivers/rtc/rtc-ds1307.c
@@ -1668,6 +1668,8 @@ static const struct watchdog_ops ds1388_wdt_ops = {
 static void ds1307_wdt_register(struct ds1307 *ds1307)
 {
 	struct watchdog_device	*wdt;
+	int err;
+	int val;
 
 	if (ds1307->type != ds_1388)
 		return;
@@ -1676,6 +1678,10 @@ static void ds1307_wdt_register(struct ds1307 *ds1307)
 	if (!wdt)
 		return;
 
+	err = regmap_read(ds1307->regmap, DS1388_REG_FLAG, &val);
+	if (!err && val & DS1388_BIT_WF)
+		wdt->bootstatus = WDIOF_CARDRESET;
+
 	wdt->info = &ds1388_wdt_info;
 	wdt->ops = &ds1388_wdt_ops;
 	wdt->timeout = 99;
-- 
2.27.0